In multistage rotary machines used for energy conversion, a fluid is used to produce rotational motion. In a gas turbine engine, for example, a gas is compressed in a compressor and mixed with a fuel source in a combustor. The combination of gas and fuel is then ignited for generating combustion gases that are directed to turbine stage(s) to produce rotational motion.
Typically, a plurality of non-rotating vane components and a plurality of rotating blade components are assembled circumferentially about an axial flow path of the engine. The vane and blade components include shroud segments that are mounted circumferentially about the axial flow path and support the respective vane and blade components. The shroud segments are typically disposed adjacent to each other in the circumferential direction such that small gaps are formed therebetween.
An outer case that surrounds the axial flow path typically includes ring segment components or blade outer air seal components and backing plate components. The outer case provides an outer radial boundary of the axial flow path. The ring segment components or blade outer air seal components and backing plate components are aligned and suspended in close proximity to blade tips of the rotating blade components to limit flow between the blade tips and the outer case. The ring segment components or blade outer air seal components and backing plate components are typically disposed adjacent to one another such that small gaps are formed therebetween.
It is desirable to prevent flow of hot combustion gases through the gaps between the adjacent components to prevent performance loss and, in particular, to prevent or limit exposure of the ring segment components and backing plate components directly to the hot combustion gases.
Some current seal designs and assemblies include sealing members such as metal strips disposed in slots which may be formed in the components. Because of the typical slot configuration, stresses are generated at relatively sharp edges. Additionally, variations in pressure forces within the engine tend to move or vibrate the components. The variable pressure may induce circumferential, radial, and/or axial movement of the components during engine operation. Accordingly, seal assemblies must be designed to tolerate such movement of the components.
Metallic type materials used to form the components have mechanical properties including strength and ductility sufficiently high to enable the components to receive and retain sealing members in the slots formed therein without resulting in substantial damage to the components during operation. However, current gas turbine engine development has suggested use of certain materials having a higher temperature capability than the metallic type materials. Such materials, such as ceramic matrix composite (CMC) or monolithic ceramic materials, have mechanical properties that must be considered during design and application of the engine components. CMC and monolithic ceramic type materials have relatively low tensile ductility or low strain to failure when compared with metallic materials. Components made from CMC or monolithic ceramic type materials, although having certain higher temperature capabilities than those of a metallic type material, may exhibit a lower tolerance to the stresses generated in the above described slots or recesses formed in the components.
In view of the foregoing considerations it would be desirable to provide a sealing element for use in a turbine engine having ceramic components, wherein the sealing element is retained in a gap formed between adjacent segments and is capable of accommodating high temperatures associated with a high velocity gas flow path of the turbine engine without substantial erosion and/or damage thereto.